1. Technical Field
The present invention is directed towards copolymers produced by solution polymerization. More particularly, the present invention is directed towards self-stabilizing copolymers having opacifying properties and processes for producing such polymers.
2. Background Information
Polymers having both hydrophobic and hydrophilic constituents such as styrene-acrylic acid copolymers are produced by a variety of processes illustrated in the art. In one process commonly referred to as solution polymerization, the copolymers are formed by polymerizing the water-insoluble monomer, e.g., styrene, and the water-soluble monomer, e.g., a carboxylated monomer, in the presence of a water miscible solvent, neutralizing the acid after the polymerization step has completed, and subsequently removing the water-miscible solvent from the solution. The polymerization step can occur in the presence of a catalyst.
In another variation of this solution polymerization process, these hydrophobic/hydrophilic type polymers are first polymerized, followed by simultaneous neutralization and distillation. Other solution polymerization processes in the art teach polymerizing at least one hydrophilic monomer and at least one hydrophobic ethylenically unsaturated monomer in a non-aqueous solvent, forming an aqueous polymer dispersion from this non-aqueous polymer solution, and subsequently adding an aqueous base or acid. While such polymers provide good soil release properties and are useful in cleaning compositions, they tend not to provide opacity to those compositions.
Emulsion polymerization is an example of another process for producing hydrophobic/hydrophilic type polymers. Such processes typically use surfactants to stabilize the emulsion. For example, processes for producing alkali-soluble emulsion copolymers of methacrylic acid and water-insoluble monomers such as styrene are known that utilize anionic and/or nonionic surfactants in an amount sufficient to stabilize the emulsion. Emulsion copolymers can be used as opacifiers in detergent, personal care and other applications. However, they tend not to provide good cleaning benefits in end use application. Consequently, other cleansing polymers are required in detergent formulations that make use of such emulsion copolymers.
Accordingly, there is a need for polymeric ingredients or compounds that are useful in cleaning compositions while also providing opacity to those compositions. Further, there is a need for dispersion polymers that are self-stabilizing.